With concern about infection, transmission of AIDS, hepatitis and similar incurable diseases of the blood, methods and devices to enclose the used disposable needle tip have become very important and in great demand. Many approaches to guard the needle, protect users and/or otherwise prevent injury have been proposed. All of them are cumbersome, expensive and interfere with the normal and accepted procedure for the insertion of an over the needle catheter. Typical of such introducers is U.S. Pat. No. 4,846,805 wherein the shield slides over the flash chamber body to engage the catheter and lock about the used needle tip.
Specifically, after the catheter has been inserted by an over the needle procedure and blood flashback has been observed, the catheter is advanced and/or the needle is withdrawn. After the catheter is inserted into the vessel as desired and the needle is withdrawn and discarded, protection of the used needle tip is important. Cumbersome needle guards interfere with the single hand over the needle catheter placement procedure. The needle tip cover disclosed herein does not interfere with or require any additional mechanisms which interfere with the accepted over the needle technique.
U.S. Pat. No. 4,139,009 has a needle tip protector with a permanently attached cover surrounding the needle and a number of elastic arms which extend along the length of the needle. The arms are constructed so as to bow outwardly from the needle shank when the needle is pressed against and into the patient. U.S. Pat. No. 4,660,570 shows a needle tip protector with a membrane extending over the sharp point of the needle whereby penetration causes the needle to extend through the membrane and the skin of the patient.
U.S. Pat. No. 4,650,468 has a device with a sleeve concentrically placed about the needle shank. A safety shield at one end has a rubber membrane extending across an opening in the shield. The membrane is adapted to be pierced by the needle tip for use.
U.S. Pat. No. 2,828,744 discloses a flexible needle assembled from an enlarged metal end and a resilient tube. The metal end and the resilient tube have different diameters. The idea behind this patent is to provide a flexible tube that can be left in the blood vessel and the two piece assembly is for that purpose. U.S. Pat. No. 4,250,881 discloses a needle having an end that is spread so as to prevent the catheter coaxially placed on the needle proximal of the end from experiencing compressive loads during insertion. The catheter is soft and the idea is to prevent the bunching or accordion like folding of the catheter due to the penetration of the tissue.
There is no teaching or disclosure of anything which provides the diameter change with a particular geometry found to retain a needle tip cover from removal over the needle tip and yet with a needle which has such a small change in shape that there appears to be no perceptible shape change. The idea of having to be the recipient of an enlarged needle tip during a catheter insertion or the like is offensive to most people. The problem of changing the diameter imperceptably is resolved herein.